1. Field of the Invention
The present invention relates to a pulse encoder having a circuit for diagnosing abnormalities and more particlularly to an optical pulse encoder employing light-emitting diodes (hereinafter referred to as LEDs), the pulse encoder having a circuit for detecting abnormalities such as the breaking of wire in LEDs, lowering of the voltage applied to the pulse encoder, a problem in an output transistor in a signal-outputting element, and so forth.
2. Description of the Prior Art
Generally, a pulse encoder detects the angle of rotation and the rotating speed of a motor, and a numerical control device receives the detected outputs from the pulse encoder. The numerical control device controls the angle of rotation and the rotating speed of the motor in accordance with the detected outputs from the pulse encoder so that a load coupled to the axle of the motor is positioned in a desired position.
In the pulse encoder, however, when an above-mentioned abnormality occurs, the output signal of the pulse encoder becomes indefinite. If the numerical control device receives an indefinite signal from the pulse encoder, it cannot control the angle of rotation and the rotating speed of the motor, resulting in uncontrolled running of the numerical control device or the motor.
A conventional pulse encoder does not have a circuit for detecting the above-mentioned abnormalities. Therefore, uncontrolled running of the numerical control device or the motor often occurs.